Double stranded DNA viruses such as adenovirus, the herpesviruses, and several bacteriophages contain a class of enzymes called terminases that function to insert (package) the viral genome into a preformed capsid. This is a critical step in the virus lifecycle, and therefore presents an attractive target for the development of antiviral drugs. Bacteriophage lambda is an ideal model system to study viral DNA packaging mechanisms due to the availability of a large amount of biochemical and genetic data. The long-term goal of this project is to understand the mechanistic details of how lambda terminase processes the viral genome to form a DNA packaging motor. Within this context, the specific aims of this project are to determine the assembly state of lambda terminase both in solution and when in complex with viral DNA, and to define a minimal kinetic mechanism that describes the lambda terminase catalyzed DNA processing reactions that lead to genome packaging.